This invention pertains to radios.
Two-way radios have a number of operating parameters including, but not limited to, transmitting power, operating frequencies (channel), operating band modulation type, modulation index, frequency deviation, squelch setting, channel spacing, control channel (for trunked communications), noise blanker characteristic, and receive bandwidth. Of these parameters, some are fixed, while others may be, to some degree, variable. One example of a parameter which is usually, but not always, fixed is the modulation type, such as FM or AM. One example of a parameter which is usually, but not always, favorable is the operating frequency or frequencies (channel).
At a given time, it may be desirable to adjust the operating parameters in response to the current operating environment to obtain optimum performance. For example, it may be desirable to minimize interference to other users.
A significant factor in determining the current optimum operating parameters is the geographic location of the radio. As an example, a particular radio operating in a densely-populated area, such as downtown Los Angeles, Calif. must contend with, among other factors, a relatively large number of other radios using the same frequency spectrum. As a result, the available frequencies (channels) may be limited. Also, the radio must limit its transmitting power to avoid interfering with neighboring users. On the other hand, if this identical radio were located in the middle of a sparsely-populated area, such as Death Valley, Calif., it would contend with few (if any) other radios using the same frequency spectrum. As a result, more channels are available and the transmitting power may be increased to achieve greater range without interfering with neighboring users.
For radios which are fixed in location, that is, non-mobile, usually there are few parameters, if any, which need to be varied during day-to-day operation. This is because the operating environment is relatively constant for the radio which is due, to a large extent, to the fact that the location of the radio is fixed.
For radios whose location is not fixed (that is, mobile), on the other hand, it is desirable for operating parameters to be adjusted whenever a change in the location of the radio causes the operating environment to change. For example, using the above example, if a mobile radio initially selects an operating frequency band and transmit power while it is located in downtown Los Angeles, the radio may need to periodically adjust (change) these frequency band and power settings as its location constantly changes during the course of its journey from the downtown area to a final destination of Death Valley, Moreover, it also may be advantageous to change other operating parameters during the course of such a journey.
Another situation where a mobile radio might need to adjust operating parameters based on its location arises in trunked radio systems. In such systems, many subscriber units share a fixed (and typically smaller) number of communication channels. In such systems, a common control station uses a control channel to allocate the shared channels amongst the subscriber units. When a subscriber wishes to place a call, it first tunes to the control channel and transmits a channel request message to the control station. Upon receipt of this message (and assuming an idle channel is available) the controls station reserves, or assigns, an idle channel for the call. The control station then transmits the channel assignment information to the requesting subscriber via the control channel. Upon receipt of this channel assignment message, the requesting subscriber unit tunes to the assigned channel and proceeds to place its call.
In general, then, it is desirable for a mobile radio to have the ability to change operating parameters based on its current location. Given this fact, the question arises of how to effect the desired changes in the operating parameters. While it is obvious the human operator could manually adjust the operating parameters to obtain optimum performance, this could also prove to be risky. This is because, due to human error, the operator may be mistaken as to either the present location of the radio, or the current optimum operating parameters for the present location of the radio, or both.